Fix #2257: Add global:: prefix, iff the containing namespace matches the type name.

ICSharpCode.Decompiler/CSharp/Syntax/TypeSystemAstBuilder.cs

@@ -525,14 +525,13 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 				// Handle top-level types
 				if (string.IsNullOrEmpty(genericType.Namespace))
 				{
-					result.Target = new SimpleType("global");
-					if (AddResolveResultAnnotations && resolver != null)
-						result.Target.AddAnnotation(new NamespaceResolveResult(resolver.Compilation.RootNamespace));
+					result.Target = MakeGlobal();
 					result.IsDoubleColon = true;
 				}
 				else
 				{
-					result.Target = ConvertNamespace(genericType.Namespace, out _);
+					result.Target = ConvertNamespace(genericType.Namespace,
+						out _, genericType.Namespace == genericType.Name);
 				}
 			}
 			result.MemberName = genericType.Name;
@@ -605,6 +604,11 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 		}
 
 		public AstType ConvertNamespace(string namespaceName, out NamespaceResolveResult nrr)
+		{
+			return ConvertNamespace(namespaceName, out nrr, requiresGlobalPrefix: false);
+		}
+
+		AstType ConvertNamespace(string namespaceName, out NamespaceResolveResult nrr, bool requiresGlobalPrefix)
 		{
 			if (resolver != null)
 			{
@@ -633,18 +637,27 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 			{
 				if (IsValidNamespace(namespaceName, out nrr))
 				{
-					var ns = MakeSimpleType(namespaceName);
+					AstType ns;
+					if (requiresGlobalPrefix)
+					{
+						ns = new MemberType {
+							Target = MakeGlobal(),
+							IsDoubleColon = true,
+							MemberName = namespaceName
+						};
+					}
+					else
+					{
+						ns = MakeSimpleType(namespaceName);
+					}
 					if (AddResolveResultAnnotations && nrr != null)
 						ns.AddAnnotation(nrr);
 					return ns;
 				}
 				else
 				{
-					var target = new SimpleType("global");
-					if (AddResolveResultAnnotations)
-						target.AddAnnotation(new NamespaceResolveResult(resolver.Compilation.RootNamespace));
 					var ns = new MemberType {
-						Target = target,
+						Target = MakeGlobal(),
 						IsDoubleColon = true,
 						MemberName = namespaceName
 					};
@@ -661,7 +674,7 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 			{
 				string parentNamespace = namespaceName.Substring(0, pos);
 				string localNamespace = namespaceName.Substring(pos + 1);
-				var parentNS = ConvertNamespace(parentNamespace, out var parentNRR);
+				var parentNS = ConvertNamespace(parentNamespace, out var parentNRR, requiresGlobalPrefix);
 				var ns = new MemberType {
 					Target = parentNS,
 					MemberName = localNamespace
@@ -695,6 +708,14 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 			return new SimpleType(name);
 		}
 
+		SimpleType MakeGlobal()
+		{
+			var global = new SimpleType("global");
+			if (AddResolveResultAnnotations && resolver != null)
+				global.AddAnnotation(new NamespaceResolveResult(resolver.Compilation.RootNamespace));
+			return global;
+		}
+
 		static MemberType MakeMemberType(AstType target, string name)
 		{
 			if (name == "_")

ILSpy/Languages/CSharpHighlightingTokenWriter.cs

@@ -144,7 +144,6 @@ namespace ICSharpCode.ILSpy
 				case "for":
 				case "foreach":
 				case "lock":
-				case "global":
 				case "await":
 					color = structureKeywordsColor;
 					break;
@@ -343,8 +342,18 @@ namespace ICSharpCode.ILSpy
 			{
 				color = valueKeywordColor;
 			}
-			if (identifier.Name == "var" && identifier.Parent is AstType)
-				color = queryKeywordsColor;
+			if (identifier.Parent is AstType)
+			{
+				switch (identifier.Name)
+				{
+					case "var":
+						color = queryKeywordsColor;
+						break;
+					case "global":
+						color = structureKeywordsColor;
+						break;
+				}
+			}
 			switch (GetCurrentDefinition())
 			{
 				case ITypeDefinition t: